My favorite is RUS. I enjoy the historical period and how you can play multiple sides. I've played the grand campaign as each faction and most of the scenarios. I've tried a few of the scenarios in TEAW and enjoyed those. I'll try some of the larger scenarios soon and eventually the campaign game.

I don't play a lot but I've played RUS the most, followed by TEAW. I got most of my games through a sale and haven't gotten around to playing most of them yet but I'm sure I'll get to CW2 at some point.